1. Field of the Invention
The present invention relates to a thin film magnetic head provided, for example, on the trailing edge portion of a slider facing a magnetic recording medium. In particular, the present invention relates to a thin film magnetic head exhibiting reduced thermal expansion due to heat release from a coil used for a recording head portion.
2. Description of the Related Art
As shown in FIG. 11, a conventional thin film magnetic head is provided with a recording head portion h85 on a trailing-side edge surface 81a of a slider 81. This recording head portion h85 is an inductive head provided with a first coil 84 and a second coil 86 between a lower core layer 82 and an upper core layer 83. A joint 87 is arranged between the lower core layer 82 and the upper core layer 83, and the lower core layer 82 and the upper core layer 83 are magnetically connected by the joint 87.
The first coil 84 is formed from a conductive layer wound around the joint 87 for magnetically connecting the lower core layer 82 and the upper core layer 83. A recording portion 85 is arranged outside the first coil 84, and the recording portion 85 includes a magnetic pole portion 85a magnetically connected to the upper core layer 83 and a magnetic gap layer 85b made of an insulating material between the aforementioned lower core layer 82 and the magnetic pole portion 85a. 
The space between the conductive layers constituting the first coil 84 is filled in with an organic insulating layer 88. Furthermore, the aforementioned organic insulating layer 88 is covered with an inorganic insulating film 89 made of Al2O3.
The top surface of the inorganic insulating film 89 is flattened by polishing, and the aforementioned second coil 86 is arranged on the inorganic insulating film 89. The second coil 86 is electrically connected to the first coil 84.
In a magnetic recorder equipped with a hard magnetic disk, when the recording head portion h85 magnetically records to the magnetic disk serving as a magnetic medium, the slider 81 floats above the magnetic disk with a very small clearance.
A recording current is applied to the first coil 84 and the second coil 86, magnetic fields induced by the recording current to the lower and upper core layers 82 and 83 are applied to the magnetic disk as a leakage flux with the magnetic gap layer 85b of the recording portion 85 therebetween, and information is recorded on the magnetic disk.
In such a conventional thin film magnetic head, the organic insulating layer 88 expands due to the heat release from the first coil 84, and thereby, the recording head portion h85 protrudes from the facing-surface 81b of the slider 81 facing the recording medium at the portion of the organic insulating layer 88.
In particular, regarding a thin film magnetic head capable of achieving a high packing density, since the frequency of the recording current applied to the first coil 84 is high, the heating of the first coil 84 is increased. As the heating of the first coil 84 is increased, the thermal expansion of the organic insulating layer 88 becomes significant, and the amount of protrusion of the recording head portion h85 is increased.
Regarding a magnetic recorder capable of achieving a high-density, high-speed recording, the spacing between the magnetic medium and the facing-surface 81b of the slider 81 facing thereto is reduced, and therefore, when the recording head portion h85 protrudes, the frequency of hitting the recording head portion h85 against the magnetic medium is increased. Consequently, the recording medium is likely to be damaged, or the recording head portion h85 is likely to be damaged.